With the development of technology, a capacity, an energy consumption, and a accessing speed of the conventional NAND flash memory have reached bottlenecks.
A resistive random access memory (RRAM) is a new non-volatile random access memory. Its principle is to use a resistance mutation of a special metal oxide near a threshold voltage to represent 0 and 1 of a storage unit. RRAM has characteristics of larger capacity, lower energy consumption and faster accessing speed.
A basic storage unit of the RRAM includes two metal layers and a resistance layer sandwiched between the two metal layers. Conventionally, the resistance layer is made of WOx. A manufacturing process is compatible with a conventional MOS process. The manufacturing process includes: filling a tungsten plug on a base metal, grinding and oxidizing the tungsten metal, then forming a metal layer.
However, there are problems in the manufacturing process, which leads to an uneven distribution of resistance on the wafer.